This study will evaluate the utility of the polymerase chain reaction (PCR) for longitudinal testing of health care workers for evidence of exposure to the Human Immunodeficiency Virus Type 1 (HIV-1). Rarely, health care workers working with persons infected with HIV-1 and laboratory personnel working with blood, serum and cultures containing HIV-1 have been infected with the virus through accidents on the job, usually by penetrating injuries or mucosal exposure. The PCR is a recently developed test that can detect proviral sequences of HIV-1 prior to the time when antibodies to the virus are produced. The results of the PCR will be compared to the ELISA, Western Blots and p24 antigen capture assays performed on the same subjects in order to determine the sensitivity of the PCR compared to the standard serologic tests for predicting early infection with HIV-1 in this low-risk population. Upper confidence limits for the risk of infection in this population will be established.